Implications of the cosmic-ray radial intensity gradients observed during minimum solar modulation

1968 ◽  
Vol 46 (10) ◽  
pp. S946-S949 ◽  
Author(s):  
J. J. O'Gallagher
Keyword(s):  
Diffusion Coefficient ◽  
Solar Cycle ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
Solar Modulation ◽  
Space Probe ◽  
Magnetic Rigidity ◽  
A Value ◽  
Particle Parameters ◽  
Gradient Measurements

We have already reported the cosmic-ray radial intensity gradients for both protons and helium nuclei measured over two decades in Rβ (magnetic rigidity R times velocity β) on the Mariner IV space probe in 1965 which showed that the modulating function is separable into the product of a function of particle parameters and a function of the time t and the heliocentric radius r for the observations (O'Gallagher and Simpson 1967). The modulating function can be written as exp (−η(r, t)/ƒ(R, β)) where η(r, t) is the modulating parameter and ƒ(R, β) = Rβ for [Formula: see text] and ƒ(R, β) [Formula: see text] β for [Formula: see text]. The magnitude of the observed gradient corresponds to a change Δη = −0.2 ± 0.05 GV for Δr = 0.4 AU and at 1 GV yields a value for the diffusion coefficient in Parker's model of 3.2 × 1021 cm/s. If the value of η in 1965 is small [Formula: see text], the observed value of Δη/Δr implies that the greatest part of the modulation takes place within 5 AU at solar minimum. The value of Δη; derived from these gradient measurements is compared with estimates of the change in η required to produce the observed time–intensity variations during the solar cycle.

scholarly journals Cosmic ray recovery and solar minimum phase of solar cycle 22: An interim report

1998 ◽  
Vol 103 (A1) ◽  
pp. 373-379 ◽  
Author(s):  
Frank B. McDonald ◽  
Nand Lal ◽  
Robert E. McGuire
Keyword(s):  
Solar Cycle ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
Minimum Phase ◽  
Interim Report

Low-energy cosmic-ray heavy nuclei during the time of solar minimum

1968 ◽  
Vol 46 (10) ◽  
pp. S598-S600
Author(s):  
E. Tamai ◽  
M. Tsubomatsu ◽  
K. Ogura
Keyword(s):  
Energy Range ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
Low Energy ◽  
Energy Spectra ◽  
Solar Modulation ◽  
Atmospheric Depth ◽  
Heavy Nuclei ◽  
Multiply Charged ◽  
Α Particles

Nuclear emulsions were exposed at 2.3 g cm−2 atmospheric depth over Fort Churchill in 1965. These emulsions have been examined for the tracks of multiply-charged [Formula: see text] nuclei, with emphasis being paid particularly to those particles that stopped in the emulsions. Differential energy spectra of α particles and [Formula: see text], [Formula: see text]and [Formula: see text] nuclei were obtained in the energy interval 60–550 MeV/nucleon. They represent experimental results during the period when solar modulation effects were at a minimum. The fluxes of α particles and L, M, and H nuclei for energy intervals of 60–170, 100–400, 100–525, and 140–550 MeV/nucleon were found to be 20.9 ± 1.2, 2.4 ± 0.4, 4.8 ± 0.6, and 2.5 ± 0.4 particles m−2 sr−1 s−1, respectively. The results also show that the L/M and H/M ratios at the top of the atmosphere were 0.56 ± 0.16 and 0.34 ± 0.13 respectively, in the energy range from 140 to 350 MeV/nucleon. These values are appreciably greater than those observed at higher energies.

Solar modulation of galactic cosmic rays near solar minimum (1965)

1968 ◽  
Vol 46 (10) ◽  
pp. S887-S891 ◽  
Author(s):  
V. K. Balasubrahmanyan ◽  
D. E. Hagge ◽  
F. B. McDonald
Keyword(s):  
Cosmic Rays ◽  
Solar Minimum ◽  
Intensity Variation ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Solar Modulation ◽  
Time Behavior ◽  
Cosmic Ray Intensity ◽  
Radial Gradient

The results of the continuous monitoring of the intensity of cosmic rays (of energy > 50 MeV) with identical G-M counter telescopes flown in satellites IMP I, II, and III and OGO-I are presented along with the differential spectrum studies obtained from balloon flights at Fort Churchill and from satellites. A comparison of the time behavior of the G-M counter data with Deep River neutron monitor data suggests the presence of a "hysteresis" type of behavior due to spectral changes occurring near solar minimum. The existence of this "hysteresis" suggests that the radial gradient of cosmic rays near the earth could be much smaller than the ~ 10%/AU obtained by O'Gallagher and Simpson (1967) and O'Gallagher (1967) at higher energies. The long-term intensity variation of cosmic rays seems to follow the Ap index rather closely in phase, in contrast to sunspot numbers which display a pronounced phase difference with cosmic-ray intensity. The differential spectra of protons and He nuclei have been analyzed in terms of two different models for the propagation in the interplanetary medium. The modulations indicated by the present data seem to disagree with a diffusion coefficient proportional to βR where β and R are the velocity and rigidity of the particle respectively (Jokipii 1966).

scholarly journals Features of the Galactic Cosmic Ray Anisotropy in Solar Cycle 24 and Solar Minima 23/24 and 24/25

Solar Physics ◽  
2019 ◽  
Vol 294 (10) ◽  
Author(s):  
R. Modzelewska ◽  
K. Iskra ◽  
W. Wozniak ◽  
M. Siluszyk ◽  
M. V. Alania
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
Radial Component ◽  
Galactic Cosmic Rays ◽  
Positive Polarity ◽  
Heliospheric Magnetic Field ◽  
Solar Cycle 24 ◽  
Cycle 24

Abstract We study the role of the drift effect in the temporal changes of the anisotropy of galactic cosmic rays (GCRs) and the influence of the sector structure of the heliospheric magnetic field on it. We analyze the GCR anisotropy in Solar Cycle 24 and solar minimum 23/24 with negative polarity ($qA<0$qA<0) for the period of 2007 – 2009 and near minimum 24/25 with positive polarity ($qA>0$qA>0) in 2017 – 2018 using data of the global network of Neutron Monitors. We use the harmonic analysis method to calculate the radial and tangential components of the anisotropy of GCRs for different sectors (‘+’ corresponds to the positive and ‘−’ to the negative directions) of the heliospheric magnetic field. We compare the analysis of GCR anisotropy using different evaluations of the mean GCRs rigidity related to Neutron Monitor observations. Then the radial and tangential components are used for characterizing the GCR modulation in the heliosphere. We show that in the solar minimum 23/24 in 2007 – 2009 when $qA<0$qA<0, the drift effect is not visibly evident in the changes of the radial component, i.e. the drift effect is found to produce $\approx 4$≈4% change in the radial component of the GCR anisotropy for 2007 – 2009. Hence the diffusion dominated model of GCR transport is more acceptable in 2007 – 2009. In turn, near the solar minimum 24/25 in 2017 – 2018 when $qA>0$qA>0, the drift effect is evidently visible and produces ≈40% change in the radial component of the GCR anisotropy for 2017 – 2018. So in the period of 2017 – 2018 a diffusion model with noticeably manifested drift is acceptable. The results of this work are in good agreement with the drift theory of GCR modulation, according to which, during negative (positive) polarity cycles, a drift stream of GCRs is directed toward (away from) the Sun, thus giving rise to a 22-year cycle variation of the radial GCR anisotropy.

scholarly journals Measurements of the time-dependent cosmic-ray Sun shadow with seven years of IceCube data: Comparison with the Solar cycle and magnetic field models

2021 ◽  
Vol 103 (4) ◽  
Author(s):  
M. G. Aartsen ◽  
R. Abbasi ◽  
M. Ackermann ◽  
J. Adams ◽  
J. A. Aguilar ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Cosmic Ray ◽  
Time Dependent ◽  
Data Comparison

Solar-cycle phenomena in cosmic-ray intensity: Differences between even and odd cycles

1988 ◽  
Vol 42 (3) ◽  
pp. 233-244 ◽  
Author(s):  
H. Mavromichalaki ◽  
E. Marmatsouri ◽  
A. Vassilaki
Keyword(s):  
Solar Cycle ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity ◽  
Odd Cycles

scholarly journals Measurement of Low-Energy Cosmic-Ray Antiprotons at Solar Minimum

1998 ◽  
Vol 81 (19) ◽  
pp. 4052-4055 ◽  
Author(s):  
H. Matsunaga ◽  
S. Orito ◽  
H. Matsumoto ◽  
K. Yoshimura ◽  
A. Moiseev ◽  
...  
Keyword(s):  
Solar Minimum ◽  
Cosmic Ray ◽  
Low Energy

scholarly journals Successive measurements of cosmic-ray antiproton spectrum in a positive phase of the solar cycle

2001 ◽  
Vol 16 (2) ◽  
pp. 121-128 ◽  
Author(s):  
T. Maeno ◽  
S. Orito ◽  
H. Matsunaga ◽  
K. Abe ◽  
K. Anraku ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Cosmic Ray ◽  
Positive Phase

Induced polarization and pore radius — A discussion

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. D519-D526 ◽  
Author(s):  
Andreas Weller ◽  
Zeyu Zhang ◽  
Lee Slater ◽  
Sabine Kruschwitz ◽  
Matthias Halisch
Keyword(s):  
Diffusion Coefficient ◽  
Relaxation Time ◽  
Diffusion Coefficients ◽  
Pore Radius ◽  
Mercury Porosimetry ◽  
Induced Polarization ◽  
Reliable Estimate ◽  
Characteristic Relaxation Time ◽  
A Value ◽  
Apparent Diffusion

Permeability estimation from induced polarization (IP) measurements is based on a fundamental premise that the characteristic relaxation time [Formula: see text] is related to the effective hydraulic radius [Formula: see text] controlling fluid flow. The approach requires a reliable estimate of the diffusion coefficient of the ions in the electrical double layer. Others have assumed a value for the diffusion coefficient, or postulated different values for clay versus clay-free rocks. We have examined the link between a widely used single estimate of [Formula: see text] and [Formula: see text] for an extensive database of sandstone samples, in which mercury porosimetry data confirm that [Formula: see text] is reliably determined from a modification of the Hagen-Poiseuille equation assuming that the electrical tortuosity is equal to the hydraulic tortuosity. Our database does not support the existence of one or two distinct representative diffusion coefficients but instead demonstrates strong evidence for six orders of magnitude of variation in an apparent diffusion coefficient that is well-correlated with [Formula: see text] and the specific surface area per unit pore volume [Formula: see text]. Two scenarios can explain our findings: (1) the length scale defined by [Formula: see text] is not equal to [Formula: see text] and is likely much longer due to the control of pore-surface roughness or (2) the range of diffusion coefficients is large and likely determined by the relative proportions of the different minerals (e.g., silica and clays) making up the rock. In either case, the estimation of [Formula: see text] (and hence permeability) is inherently uncertain from a single characteristic IP relaxation time as considered in this study.

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